This project is concerned with metabolic alterations in the brain which occur in experimentally produced amino acid imbalances. Investigations are being carried out on the effects of various acute and chronic hyperaminoacidemias on regulatory mechanisms for amino acid and protein metabolism in rat brain. The specific phenomena studied include: (a) developmental and regional differences in the sensitivity of the brain to alterations in amino acid distribution resulting from amino acid loading, (b) the relationship of the resulting amino acid imbalance to variations in the properties of brain protein-synthesizing systems, and (c) the basic metabolic mechanisms underlying these processes.